1. Field of the Invention
This invention pertains generally to computer joysticks and position controllers, and more particularly to a multi-axial position sensing apparatus for joysticks and position controllers in which Hall-effect sensors and magnets pivot to provide an output voltage proportional to angle of rotation and a polarity relative to direction of rotation.
2. Description of the Background Art
Joysticks, position controllers and the like are widely used to control computers and machinery. Such devices are generally classified as either on/off devices or proportional devices. On/off devices only provide an indication of whether displacement of the joystick has occurred, whereas proportional devices provide output signals having a magnitude indicative of the amount of displacement that has occurred. The devices may be either connected directly to the device to be controlled through a mechanical linkage, or provide output signals which are received by the device to be controlled and processed into the corresponding control functions.
To overcome common problems associated with mechanical linkages between the joystick and the device to be controlled, most joysticks now produce electrical signals to indicate joystick movement. In such devices, sensors are employed to detect displacement of the joystick. The sensors generate electrical signals upon movement of the joystick which are sent to the device to be controlled, or which activate intermediate relays, motors and the like. However, even though electronic joysticks overcome common problems associated with mechanical linkages, the sensors traditionally used have been mechanical switches and potentiometers which suffer from wear, breakage, loss of accuracy and similar problems. Therefore, there has been a trend toward contactless joysticks.
A commonly used contactless joystick employs Hall-effect sensors and magnets. By changing the distance between a magnet and a Hall-effect sensor the output voltage of the sensor will change. Thus, movement of the joystick is detected by a change in output voltage resulting from a change in relative position between the magnet and the Hall-effect sensor. However, a difficulty often encountered in such devices is ensuring that a reasonable strength from the magnet is present at the sensor over the entire range of joystick movement. Another problem is that Hall-effect sensors can suffer from saturation effects when subjected to high magnetic fields and, therefore, discrimination between small displacements of joystick movement can be difficult. Also, in order to detect motion in the +x, -x, +y and -y directions, as well as in intermediate directions, at least four sensors or magnets have been required and some joysticks have employed as many as seven sensors. This results in increased cost, size and difficulty in maintaining sensor calibration.
Therefore, there is a need for a multi-axial position sensing apparatus which employs as few contactless sensors as possible, which is compact, and which provides for a high degree of repeatability and accuracy. The present invention satisfies those needs, as well as others, and overcomes deficiencies found in conventional devices.